Buggy code:
private List < LuceneTestCase . UncaughtExceptionEntry > uncaughtExceptions = Collections . synchronizedList ( new ArrayList < LuceneTestCase . UncaughtExceptionEntry > ( ) ) ; private static String savedDefaultCodec ; private static Codec codec ; private static CodecProvider savedCodecProvider ; private static Locale locale ; private static Locale savedLocale ; private static TimeZone timeZone ; private static TimeZone savedTimeZone ; protected static Map < MockDirectoryWrapper , StackTraceElement [ ] > stores ; private static final String [ ] TEST_CODECS = new String [ ] { "MockSep" , "MockFixedIntBlock" , "MockVariableIntBlock" , "MockRandom" } ; private static void swapCodec ( Codec c , CodecProvider cp ) { } static Codec installTestCodecs ( String codec , CodecProvider cp ) { } static void removeTestCodecs ( Codec codec , CodecProvider cp ) { } static String pickRandomCodec ( Random rnd ) { } @ Deprecated static List < String > testClassesRun = new ArrayList < String > ( ) ; private static void initRandom ( ) { } @ Deprecated private static boolean icuTested = false ; @ BeforeClass public static void beforeClassLuceneTestCaseJ4 ( ) { } @ AfterClass public static void afterClassLuceneTestCaseJ4 ( ) { } protected static boolean testsFailed ; @ Rule public final TestWatchman intercept = new TestWatchman ( ) { @ Override public void failed ( Throwable e , FrameworkMethod method ) { } @ Override public void starting ( FrameworkMethod method ) { } } ; @ Before public void setUp ( ) throws Exception { } protected void purgeFieldCache ( final FieldCache fc ) { } protected String getTestLabel ( ) { } @ After public void tearDown ( ) throws Exception { } private static final int THREAD_STOP_GRACE_MSEC = 50 ; private static final IdentityHashMap < Thread , Boolean > rogueThreads = new IdentityHashMap < Thread , Boolean > ( ) ; private static int threadCleanup ( String context ) { } protected void assertSaneFieldCaches ( final String msg ) { } public static int atLeast ( Random random , int i ) { } public static int atLeast ( int i ) { } public static boolean rarely ( Random random ) { } public static boolean rarely ( ) { } public static boolean usually ( Random random ) { } public static boolean usually ( ) { } @ Deprecated public static void assertEquals ( double expected , double actual ) { } @ Deprecated public static void assertEquals ( String message , double expected , double actual ) { } @ Deprecated public static void assertEquals ( float expected , float actual ) { } @ Deprecated public static void assertEquals ( String message , float expected , float actual ) { } public static void assumeTrue ( String msg , boolean b ) { } public static void assumeFalse ( String msg , boolean b ) { } public static void assumeNoException ( String msg , Exception e ) { } public static < T > Set < T > asSet ( T ... args ) { } public static void dumpIterator ( String label , Iterator < ? > iter , PrintStream stream ) { } public static void dumpArray ( String label , Object [ ] objs , PrintStream stream ) { } public static IndexWriterConfig newIndexWriterConfig ( Version v , Analyzer a ) { } public static IndexWriterConfig newIndexWriterConfig ( Random r , Version v , Analyzer a ) { IndexWriterConfig c = new IndexWriterConfig ( v , a ) ; if ( r . nextBoolean ( ) ) { c . setMergeScheduler ( new SerialMergeScheduler ( ) ) ; } if ( r . nextBoolean ( ) ) { if ( LuceneTestCase . rarely ( r ) ) { c . setMaxBufferedDocs ( _TestUtil . nextInt ( r , 2 , 7 ) ) ; } else { c . setMaxBufferedDocs ( _TestUtil . nextInt ( r , 8 , 1000 ) ) ; } } if ( r . nextBoolean ( ) ) { if ( LuceneTestCase . rarely ( r ) ) { <START_BUG> c . setTermIndexInterval ( ( LuceneTestCase . random . nextBoolean ( ) ? _TestUtil . nextInt ( r , 1 , 31 ) : _TestUtil . nextInt ( r , 129 , 1000 ) ) ) ; <END_BUG> } else { c . setTermIndexInterval ( _TestUtil . nextInt ( r , 32 , 128 ) ) ; } } if ( r . nextBoolean ( ) ) { c . setIndexerThreadPool ( new ThreadAffinityDocumentsWriterThreadPool ( _TestUtil . nextInt ( r , 1 , 20 ) ) ) ; } if ( r . nextBoolean ( ) ) { c . setMergePolicy ( LuceneTestCase . newTieredMergePolicy ( ) ) ; } else if ( r . nextBoolean ( ) ) { c . setMergePolicy ( LuceneTestCase . newLogMergePolicy ( ) ) ; } else { c . setMergePolicy ( new MockRandomMergePolicy ( r ) ) ; } c . setReaderPooling ( r . nextBoolean ( ) ) ; c . setReaderTermsIndexDivisor ( _TestUtil . nextInt ( r , 1 , 4 ) ) ; return c ; } public static LogMergePolicy newLogMergePolicy ( ) { } public static TieredMergePolicy newTieredMergePolicy ( ) { } public static LogMergePolicy newLogMergePolicy ( Random r ) { } public static TieredMergePolicy newTieredMergePolicy ( Random r ) { } public static LogMergePolicy newLogMergePolicy ( boolean useCFS ) { } public static LogMergePolicy newLogMergePolicy ( boolean useCFS , int mergeFactor ) { } public static LogMergePolicy newLogMergePolicy ( int mergeFactor ) { } public static MockDirectoryWrapper newDirectory ( ) throws IOException { } public static MockDirectoryWrapper newDirectory ( Random r ) throws IOException { } public static MockDirectoryWrapper newDirectory ( Directory d ) throws IOException { } public static MockDirectoryWrapper newFSDirectory ( File f ) throws IOException { } public static MockDirectoryWrapper newFSDirectory ( File f , LockFactory lf ) throws IOException { } public static MockDirectoryWrapper newDirectory ( Random r , Directory d ) throws IOException { }

Fix:
c . setTermIndexInterval ( ( r . nextBoolean ( ) ? _TestUtil . nextInt ( r , 1 , 31 ) : _TestUtil . nextInt ( r , 129 , 1000 ) ) ) ;